On interspecific mating in Phengodes and inbreeding in Eros. (Coleoptera)

32 PEOCEEDINGS

ENTOMOLOGICAL

SOCIETY

Perdita punctiferan. sp.

Female. Runs in

my

^{table inProc. Phila.} Acad., 1896, toP. mentzelice Ckll.,towhichitisnearlyrelated, differingbythewhitelateralfacemarks being longer, and sharply pointed above, though notched on ^{inner side} (they are ^like those of P. pallidior Ckll.); the clypeus with a smallwhite spot,moreorlessdistinctly triangular, onitsupper margin;^thelightcolor of the antennae creamy-white instead ofyellow. From P. _pallidior it is

easilyknown _by the heavily banded abdomen and _largely darkened _legs, bothcharacters being^asin mentzelice.

Type: Cat. No. _16844, U. S. N.

M.

Three _specimens collected on August ^27.

Certainly ^{this insect is} very ^{close to} P. mentzelice,

and

from its

combination of characters one might suppose ^{it to} be a _hybrid, mentzelice

X

pallidior, were those species present. Further in- vestigation ^of the series of species to which this belongs will, I believe, ^elicit

some

facts of great ^interest.

The

differential char- acters

may

^{behaveinaMendelian}

manner

inhybrids,

and some

of theapparently^distinct species

may

represent the results of earlier crosses.

The

Thurberia bees _certainly do not

show any

great degree ^of modification or specialization.

The

_{impression gained} is that Thurberia

may

^{have entered the} region within comparatively recent times, ^its bee-fauna being apparentlyⁱⁿthe earlieststages of differentiation. It is singular that

we

do not find the bees which _habitually occur onother Malvaceaein the southwest.

-In connection with the papers onthe Thurberia weevil

Mr.

Barber _spoke of

two

of his breeding experiments

and

has fur- nished thefollowing abstract of ^his remarks.

ON INTERSPECIFIC MATING

IN

PHENGODES AND INBREEDING

IN

EROS.

(COLEOPTERA.)

BY HERBERT ^S. BARBER, BureauofEntomology.

The

resultsofan_experimentstartedin1912

show some

contrast totheresults ofMessrs.

Goad

andPierce in interbreedingtheThur- beria and Cotton ^Boll _Weevils, but the writer does not believe that the mere interbreeding^offorms proves^theirspecificidentity.

A

few females of a _species ofPhengodeswerereceivedthrough Mr.

CharlesSchaefferfrom

Long

Island,andtherebeingno males ofthe

same

_{species at}

hand

were confined withmalesof our local species P. laticollis.

The two

_{species appear} to live in different types ^of

OF \VASIII.\<;T<>\, VOLC.MI: \\i, ion

country, and to be _easily distinguished ⁱⁿ the male, female and larval _stages. Several males were confined, one after theother, with each female. Usually,

when

a male Uid'collix is introduced intoa_jarwith a femaleofits

own

_species,matin"-occursvery quick-

ly, but with the females of this other _species most of the male.- failed to recognize the female, and _only in a few instances dis- played sexual excitement, which

was

of short duration except ⁱⁿ two cases.

One

of thesemales attempted copulation ^a few times without success, while the other succeeded after

many

^fruitle

attempts, but displayed great difficulty in disengaging ^himself afterward. This female that had been fertilized laid eggs ⁱⁿ due time.

The

other

was

restless

and

abnormal ⁱⁿ actions, but laid three infertile eggs,

and

finally died. All the other females died without _{laying eggs.} Ofthe48 eggs ^laid by ^{the fertilized female,}

many

^{were infertile. In others the}

embryo

developed ^{but failed} to issue, and _{only ten} larvae hatched. Of these most were _very badly deformed and unable to feed.

Two

of them, however, fed and have lived fifteen

months

in confinement.

They

display the _specific characters of the male _parent. It appears from ^tin- abovethat inaddition totheisolation ofthetwo_speciesby^habital the species are separated

by

(l).lack ^of sexual attraction, (2)

mechanical difficulty in copulation, and ₍₃₎ in

some manner

the fertilizationisfaultyandresults ingross abnormalities.

The

writer believes that these two forms are very distinct species, but that chance migration ^of the malesmay. veryrarely, result ⁱⁿinterspe-

cific unions,witha _slight chanceof the survivalofhybrid offspring which would_naturallybereabsorbedinthelocal_specie-;it' ii should prove ^to be fertile.

The

_question of sexual attraction even within a single specie

is in itself a very interesting and _important question.

We

^are.

ofcourse, utterly unableto detect the difference in odors or other factors by which ^{one sex} recognizes the opposite sex ^{of its}

own

kind, and is stimulted to sexual excitement while with another species thestimulus

may

^{be absent}or repulsive.

Some

_groups ^are

sexuallymature assoonastheyhave hardenedafter issuancefrom the pupa, and

mate

with ^their

own

brothers or sisters, but most appear ^to have some obstacle (hat prevents ^breeding.

The

first

group are usually somewhat degraded and are inclined to form numerous local races or color forms.

An

_example ^{of this} group

is /-;/v>x hnnn-rnlix of which the following ^brief observation is sig-

nificant:

From

a colony^{of larva'}found last spring (1913) ^{in a}rotten syca- more log, the individuals were isolated in plaster ^cells where _they pupated and ^matured.

The

adults showed no desire for migra- tion but _{lay quiet} in thecells.

A

male was introduced into a ^cell

34 PEOCEEDINGS

ENTOMOLOGICAL

SOCIETY

with a female

and

immediately mated.

Next

_day he

was

_placed with another female and immediately mated. Both females de- positedeggs, andthe

young

beganfeeding inthewood, but^thefe- male _parents at no time displayed a ^{desire for} a migrationflight.

It is believed the colony

was

_originally from a single set of eggs

and

that

more

than

two

generations would have been _passed within the log in nature.

In the secondgroup the "provisions" against, or obstacles to ^in- breedingassumevariedforms. Usually the^ratiochanceofunions between brothers

and

sisters to unions between unrelatedindivid- uals, ^is so low that the _offspring would _{be quickly}reabsorbecl intothe normalform, but the ^{details of}habit that controlthislow percentage

may

^{be varied. Chief of these is the instinct} for mi- gration, which_appearsto precede sexual maturity ⁱⁿ

many

^social

insects, but there appears ^to be also a remarkable difference in time of development ^of the opposite ^sexes

among

^the progeny ^of a _singleparent^of

some

_species.

The

writer believesfrom_prelimi- nary experiments, that ⁱⁿ Phengodes the males _develop after two years ⁱⁿ the larval _stage, while their sisters

must

_{spend three or}

more

_years aslarvaB. In this genus themalesarestrongmigrants while the females

must

_laytheir eggswhere_theyhavetransformed.

The

writer has

shown

that inMicromalthus themales issue about

two

weeks after their sisters are _out, butsubsequent observations indicate thatmales issue abnormally ^or irregularlj^r at times. At- tempts ^to

mate

_specimens from different coloniesin the breeding

cells all failed, and as both males and females manifested only a desire to migrate from the time of their issuance almost until death, ^itis believed sexual maturity ^will develop only ^after such migratory flight.

ON THE PROPER GENERIC NAMES FOR CERTAIN THYSAN-' OPTERA OF ECONOMIC IMPORTANCE.

BY

J. DOUGLAS _HOOD, United States Biologiml Purvey.

The

tobacco _thrips, the pear thrips, and the orange thrips species responsible in the United States for

damage

amounting to

many

^{thousands ofdollars} every year and each the subject ^of several published accounts ^{are at} present wrongly placed ⁱⁿ the genusEuthrips Targioni-Tozzetti

by

^all North American workers.

The

_purposeofthispaper^{isto correct}thegeneric positions^ofthese and other allied species

and

to direct attention to several papers which have beenoverlookedinAmerica, that ^theproper

names

for these insects

may

^{be used in} the rapidly-growing economic litera- ture.